1. Field of the Invention
This invention relates to roll stand assemblies as used to form and handle sheet materials and, more particularly, to a roll stand assembly incorporating a safety assembly to maintain a gap between adjacent rolls.
2. Background Art
A multitude of roll stand assemblies currently exists to facilitate sheet formation, processing, and handling. During extrusion sheet formation, a flowable mold material is introduced at a nip location between adjacent rolls which, in addition to forming a sheet configuration, effect advancement thereof to a downstream location for further processing, joinder with other components, etc., preparatory to eventual accumulation of a final product at a point of use. There are virtually an endless number of processing, formation, and handling structures devised for such sheets. Typical of all such roll stand assemblies is the utilization of cooperating rolls that are mounted on a frame for rotation about parallel axes. Adjacent rolls have sheet engaging surfaces that cooperate throughout the manufacturing and sheet handling processes. As the processes are carried out, the cooperating rolls, in an operative state, have a predetermined gap therebetween, which is relatively small, as dictated by the particular process being carried out.
Components on roll stand assemblies typically require regular maintenance and adjustment and periodic repair. Such activities may require that the operating gap between cooperating rolls be increased so that an individual can direct his/her hand between the rolls to access certain operating components.
The gaps are typically controlled by actuating hydraulic drive components. A central controller will generally allow programming that permits an operator to selectively vary the roll gap as required. Typically, the operator will set the cooperating rolls in an open relationship to allow access therebetween. The operator relies upon the functioning of the drives to maintain the open relationship between the rolls.
Rolls on extrusion forming equipment are heavy. There always exists a possibility that under the weight of the rolls, the gap therebetween that is set with the open relationship may partially or fully close by reason of a failure of the hydraulic drives, a failure of a supporting component, or an inadvertent activation of the drives. If any of these events occur, there is a significant risk of operator injury.
Heretofore, the industry has relied primarily on the reliable performance of such drives and the controllers therefor to avoid an unintended closing of the gap between adjacent rolls in the open relationship therefor. The industry is devoid of any effective safety assemblies to prevent such occurrences. It is believed that the lack of such safety assemblies is attributable to the fact that no viable commercial design has been devised that is both effective, easy to operate, and minimally obtrusive in terms of taking up valuable space in and around the working components of the roll stand assembly.